column|empno|not_nullable|number(4)
column|ename|nullable|varchar2(10)
column|job|nullable|varchar2(9)
column|mgr|nullable|number(4)
column|hiredate|nullable|date
column|sal|nullable|number(7,2)
column|comm|nullable|number(7,2)
column|deptno|nullable|number(2)
pkey|empno
fkey|deptno|scott.dept.deptno